Controlled electrical installation for supplying arcs or other applications



y 1950 J L P G. MARTIN 2,506,964

CONTROLLED ELECTRICAL INSTALLATION FOR SUPPLYING ARCS OR OTHER APPLICATIONS Filed Aug. 8, 1947 2 Sheets-Sheet 1 INVENTOR JLF G. Mirth ATTORNEY May 1950 J. P. G. MARTIN 2,506,964

I CONTROLLED ELECTRICAL INSTALLATION FOR SUPPLYING ARCS oR OTHER APPLICATIONS Filed Aug. 8, 1947 2 Sheets-Sheet 2 Fig.2

Fig. 3

INVENTOR 11L 6. Math n an: 3m; 312 b 513 b ATTORNEY Patented May 9, 1950 CONTROLLED ELECTRICAL INSTALLATION FOR SUPPLYING ARCS OR OTHER APPLI- CATIONS Jean Louis Pierre Gabriel Martin, Paris, France Application August 8, 1947, Serial No. 767,471 In France May 25, 1946 Section 1, Public Law 690, August 8, 1946 Patent expires May 25, 1966 3 Claims. 1

Electrical installations are known for supplying utilization organs such as electric arcs comprising a control organ controlled by the utilization organ and controlling in turn the supply organ.

In such installations variable reactance coils are used acting on the supply organ through a current from a rectifier and varying with the terminal voltage of the utilization unit, variable reactance coils regulating the supply and controlled by said rectifier.

The method is also known of providing such installations with adjustable control units which can beadjusted at will by the operator independently of the action of the utilization unit.

An object of this invention is to improve these installations with a view to allowing the operation of the utilization unit in alternating current.

Electrical installations with a control for the supply of arcs and other applications make it possible to realize the above object, offering the characteristics resulting from the description given below and especially in the appended claims.

Controlled electrical installations for the supply of arcs and other applications according to the invention are represented by way of example on the appended drawings wherein:

Fig. 1 is a schematic showing of an embodiment of the invention;

Fig. 2 is a diagram of the family of static curves for the transformer of the installation of Fig. 1, showing the paths of the various starting voltages;

Fig. 3 is a diagram showing the family of dynamic curves for the transformer of the installation of Fig. 1; and

Fig. 4 is a diagram showing the characteristics of the operation resulting from the combinations of the curves in Fig. 2 and Fig. 3.

The welding apparatus shown in diagram on Figure 1 comprises a supply transformer I with a primary 2 comprising several taps I4I, I42 and I43.

The secondary of this transformer comprises three windings I33 I33 and I33 wound about a magnetic core 4.

One terminal of winding I33 is directly connected to one of the welding terminals of electrode ll while the other terminal is connected through an adjusting coil I36 to a terminal I38 of a switch I38.

The other terminal of switch I38 is interconnected with the second welding terminal II.

The other secondary coil I33 is connected respectlvely to the adjusting coil I36 and to a second adjusting coil I36 while the third secondary terminal I33 is connected on one hand to the adjusting coil I36 and on the other hand to a third adjusting coil I36 The adjusting coil I 33 is connected to contact point I38 while the adjusting coil I36 is connected to contact point I38 of the adjusting switch I 38.

To sum up, each one of the secondary windings of the supply transformer I is connected through an adjusting coil I36 I36 or I3ii to the respective contact points I38 I33 and I38 of switch This switch is mounted in such a way that when its connecting organ is on contact point I39 the secondary winding I33 and the adjusting coil I36 are alone in circuit whereas when the connecting organ is on contact point I38 winding I33 and the secondary winding I33 are mounted in series with their adjusting coils I36 and I36 Similarly, when the switch is on contact point I38 the three secondary windings I33 I33 I33 are mounted in series with the adjusting coils I36 I36 and I36 The three adjusting coils I35 I35 and I36 are wound on a magnetic circuit i35 which may be saturated under the action of a direct current flowing through saturation coils I31 I37 The saturation coil I37 is supplied through a rectifier I40 mounted in a Wheatstone bridge receiving its voltage from the terminals of the welding electrodes II.

A rheostat I4I with a contact arm I43 makes it possible to regulate the alternating voltage applied to the terminals of rectifier I48.

The saturation coil I3'I is supplied with direct current through a rectifier I43 mounted in a Wheatstone bridge to which is applied the alternating voltage from the secondary winding I33 of the supply transformer I.

A rheostat I32 mounted in series in the supply circuit for alternating current of rectifier I49 allows the adjustment of the voltage applied to the terminals of this rectifier and thereby of the current supplied by the rectifier into winding I37 It can thus be seen that the adjusting coils made up of variable reactance coils act on the supply voltage under the action of a current which is a function of the voltage at the terminals of the welding electrode l I and, similarly, of a current which is a function of the voltage across the terminals of one of the secondaries of the supply transformer I.

This arrangement serves advantageously and particularly:

1. To facilitate the ignition of the welding arc.

2. To insure the stability of this arc.

Furthermore, the use of several secondaries I33 I33 I33 which may be connected at will in series with their individual adjusting coil I36 I36 I36 makes it possible to regulate the ignition voltages to the values just necessary for each range of welding. It also makes it possible to bring the short-circuit current to the minimum value for the ignition of the arc,

Thus in the present invention ignition voltages adequately selected and automatically variable are used to facilitate the ignition of the arc.

The device, reacting to the terminal voltage of the arc, improves the ignition conditions by speeding up the build-up of the voltage necessary for the are after an excess current and particularly after the short-circuit preceding the ignition of the arc.

Also, the device insures the stability of the are for welding by compelling the voltage to follow immediately the variations of the length of the Welding arc and it even allows withinwide limits a lengthening of the arc.

This installation makes it possible to obtain a minimum consumption by decreasing the ratio open circuit voltage to voltage underload and to limit to a strict minimum the cross sections of the winding conductors which decreases the costs.

The operation of the device will be explained more fully in conjunction with the curves shown in Figures 2; 3 and 4, which curves represent the voltage across the terminals of the load as a function of the load current under various circumstances.

Figure Zrepresents the static characteristics, that is the function curves of the device of Figure 1 when the saturation coil I31 saturation of which is a function of the tension at the terminals of the Welding electrodes, does not intervene. These curves form three groups of curves, having their tops in the points Illa, H211 and Il3a, respectively and each being, enveloped by a broken line border curve and a solid line border curve as shown.

The group enclosed by the border curves Illa-lllc and lIla-lllb represent the function curves when the switch I38 is in position I38 that is when the three secondaries I33 I33 I33 of the transformer l with their respective regulating coils I36 !36 and I36 are connected in circuit with the electrodes ll. Likewise, the group of curves enclosed by the border curves ll2alllb and ll2all2b represents the function curves, when the switch I32 is in position I38 that is when the two secondaries I33 and I33 with their regulating coils i36 and I36 are connected and the group of curves enclosed by the border curves l l3a-l 12b and ll3all3b represent the function curves when the switch I38 in position I38 connects only the secondary I33 and the regulating coil I36 Which curve of a group of curves is in function is determined by the intensity of the direct current sent through the saturation coil I31 by the rectifier I49; the intensity of this current is in itself controlled by the variable resistance I32, Thus the broken line border curves lllalllc, ll2a-lllb and ll3all2b, respectively, correspond to a zero current in the coil I31 and the solid line border curves llla-ll|b, ll2a-ll2b and ll3a-ll3b corresponding to a maximum current in the coil I37 The functioning point may thus be situated between a solid line curve and a corresponding broken line curve, depending on the intensity of the direct current sent through the saturation coil I31 The functioning points I20, I21 and I22 represent the respective maximum operating welding current intensities. It will be noted that the intensity of' the short-circuiting current is appreciably higher than. the intensity of the welding current belonging to the same curve. For instance, the normal value 0a of the welding current belonging to the functioning point I22 is much, lower than the value Ob of the corresponding short-circuiting current.

Figure 3 represents the diagrammatic characteristics of the device when the saturation coil I37 does not intervene and only the saturation coil i31 of which the saturation current derived from the rectifier hill is a function of. the tension across the load, is made to operate.

Just as in Figure 2, three groups of curves are shown having their tops in the points 2i la, 212a and 2 l3a, respectively, depending. on the number of transformer secondaries I33 and regulating coils I35 put in circuit by the switch H8. The

broken line border curves2l Ear-2| lb, 2 l2a-2 l2b and 2l3a/2l3b represent the same broken line curves llla--illc, ll2all-l-b and ll 3a|l2b, respectively, of Figure 2, that is: in both cases both the coils i37 and I31 are currentless.

The solid border line curves 2| Hr-"2i lb,

2l2a-2l2b and 2l3a2i3b are the respective function curves when the saturation coil [31 is'current fed in dependence of the voltage across the welding electrodes II, the switch I43 being in its left-hand position as shown in Figure 1.

It will be noted that these curves'have a maximum in the direction of the axis of abscissa. This maximum canbe readily understood considering the fact that when the electrodes are in contact and cause a short-circuit, the tension at the terminals of the rectifier l iil'is nil and therefore the saturation current in coil. I3! is nil; the solid line curves thus coincide. with their corresponding lblOkel'l line curves in the points- 2l lb, 2 l2b and 2 l 3b, respectively. In these points the intensity of the short-circuiting current is solely determined by the reactance of the respective regulating coils I36 put in circuit, this reactance having now its maximum value, not

being diminished by the action of a saturation currentin any of the coils I31 or 131 When the welding electrodes are. separated from one another, the tension at the terminals of said welding electrodes increases so that there appears a certain saturation current in the coil I31 which causes a decrease in the. value of the reactance of the respective regulating coils l3fi. total reactance of the welding circuit decreases, which results in a fast increase in current, This increase occurs until the time when the magnetic circuit of the regulating coils I35 is saturated; from then on the solid line curves tend to approach the corresponding broken linecurves until the two again coincide at the, points Ella, M211 and 2 [3a, respectively, where-the intensity of the welding current is nil. c

As a consequence of all this it will be seen.- that the welding current intensities at thefunctioning points 220, HI and 222, for instance, are

appreciably higher than the corresponding short- Therefore, when the tensionincreases the circuiting current intensities at the points 2| lb, 2i 2b and 2l3b, respectively. Especially is this the case at the functioning point 222, having a welding current intensity Oa' as compared with the intensity Ob of the corresponding shortcircuiting current.

As will follow from this, it may happen that the curves of Figure 3, resulting from the functioning of only coil 1 31 do not provide for a short-circuiting current of sufiicient strength to insure a good ignition of the arc. On the other hand, it has been shown by the curves of Figure 2 that when only the saturation coil I31 is functioning, the short-circuiting currents may become uselessly strong.

Figure 4 shows the function of the device of Figure 1 when both rectifiers- I 49 and I40 are put in operation and therefore direct current is fed to coil l3! as well as to coil I37 The broken line curve 3| |lZ-3| lc corresponds to the broken line curve 2! la2| lb of Figure 3 and the curve Illa-l I lc of Figure 2. The solid line curves 3| la3l lb, 3l2a3l2b and 3l3a3l3b correspond respectively to the static curves Illa-l l lb, ll2al l2b, ll3a-H3b shown in Figure 2.

The points 420, 42! and 422 indicate the functioning points of the device when there occurs saturation caused by both coils I31 and I31 These points are situated outside the solid line curves because the action of the coil I31 is added to the action of the coil I31 so that they result from the combination of the corresponding solid line curves of Figures 2 and 3. Thus the welding current intensity On. at the functioning point 422 can be made equal to or only slightly diiferent from the intensity Ob of the short-circuiting current as determined by the action of coil I31 The broken line curve 3l3a422-a represents the functioning curve along which the functioning point 422 travels, when the tension at the terminals of the welding electrodes varies. It will be noted that between the points 420 and a, the current has practically a constant value.

The action of the saturation coil I3! is also favorable to the re-ignition of the arc, for at the moment the short-circuit is broken and the arc tends to reappear, the tension growing at its terminals and acting on the coil It! causes immediately an increase of the voltage through the automatic modification of the reactance of the circuit.

The switches I38 and i4! and variable resistance I32 may be controlled by a single control device, so that the adjustment of the welding current can be effected ampere by ampere from the minimum to the maximum current possible.

What is claimed is:

1. In a controlled electrical apparatus for supplying an arc or other load with alternating current, a supply transformer having separate secondary windings, a saturable reactor with several separate windings, each of said reactor windings being connected in series with one of the secondary windings of the supply transformer, whereby to form a plurality of pairs of windings, said pairs of windings being arranged to permit one of said pairs of windings to be placed in circuit separately and also being arranged to permit one pair of windings to be placed in circuit with at least one other of said pairs of windings, means for placing in circuit at least one of said pairs of windings, said means also being adapted to place at least two of said pairs of windings in circuit in series, a rectifier supplied with alter nating current by a voltage which is a function of the voltage across the arc, a saturation coil on the reactor supplied with a direct current from the said rectifier, a second rectifier supplied by the voltage across one of the secondary windings of said supply transformer, a second saturation coil on the reactor supplied by direct current from the said second rectifier, the said saturation coils and separate windings of the said reactor being mounted on the same magnetic core.

2. In a controlled electrical apparatus for supplying an are or other load with alternating current, a supply transformer having separate secondary windings, a saturable reactor with several separate windings, each of said reactor windings being connected in series with one of the secondary windings of the supply transformer, whereby to form a plurality of pairs of windings, said pairs of windings being arranged to permit one of said pairs of windings to be placed in circuit separately and also being arranged to permit one pair of windings to be placed in circuit with at least one other of said pairs of windings, means for placing in circuit at least one of said pairs of windings, said means also being adapted to place at least two of said pairs of windings in circuit in series, a rectifier supplied with alternating current by a voltage which is a function of the voltage across the arc, a rheostat connected in series in the circuit supplying said rectifier with alternating current, a saturation coil on the reactor supplied with a direct current from said rectifier, a second rectifier supplied by the voltage across one of the secondary windings of said supply transformer, a second saturation coil on the reactor supplied by direct current from the said second rectifier, the said saturation coils and separate windings of the said reactor being mounted on the same magnetic core.

3. In a controlled electrical apparatus for supplying an arc or other load with alternating current, a supply transformer having separate secondary windings, a saturable reactor with several separate windings, each of said reactor windings being connected in series with one of the secondary windings of the supply transformer, whereby to form a plurality of pairs of windings, said pairs of windings being arranged to permit one of said pairs of windings to be placed in circuit separately and also being arranged to permit one pair of windings to be placed in circuit with at least one other of said pairs of windings, means for placing in circuit at least one of said pairs of windings, said means also being adapted to place at least two of said pairs of windings in circuit in series, a rectifier supplied with alternating current by a voltage which is a function of the voltage across the arc, a saturation coil on the reactor supplied with a direct current from the said rectifier, a second rectifier supplied by the voltage across one of the secondary windings of said supply transformer, a rheostat connected in series in the circuit supplying said second rectifier with alternating current, a second saturation coil on the reactor supplied by direct current from the said second rectifier, the said saturation coils and separate windings of the said reactor being mounted on the same magnetic core.

JEAN LOUIS PIERRE GABRIEL MARTIN.

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